Sulfuric Acid Reaction Research Articles

Preparation of Multilayered Core–Shell Fe3O4-SnO2-C Nanoparticles via Polymeric/Silane–Amino Functionalization

Multilayered core–shell Fe3O4-SnO2-C nanoparticles were prepared via surface treatment and carbonization at atmospheric pressure. Fe3O4-SnO2 nanoparticles were prepared by the carboxylation of the pivotal particles (Fe3O4) with an anionic surfactant to immobilize SnO2 nanoparticles. A method was proposed to externally surround hydrophilic carbon with amine-forming materials, polyethyleneimine (PEI), and (3-Aminopropyl) triethoxysilane (APTES). The synthesis strategy was based on the electrostatic bonding of the introduced amine group with the hydroxyl group on the carbon precursor and the carbonization of the coating layer by the catalytic reaction of sulfuric acid.

Headspace Gas Chromatographic Method for Carbonate Content Determination in Layered Double Hydroxides

AbstractThe determination of carbonate content is the basic procedure for studies related to layer double hydroxides (LDHs). This paper reports a rapid and accurate headspace gas chromatographic (HS‐GC) technique for the determination of carbonate content in LDHs. The content of carbonate was expressed by the amount of CO2 generated by the reaction of sulfuric acid and carbonate, which can be measured by HS‐GC technique using a thermal conductivity detector. It was found that a complete conversion of carbonate to CO2 can be achieved at 45 °C for about 4 min and a sulfuric acid dosage of 200 μL in the headspace vial. Under optimized conditions, the limit of detection and relative standard deviation of HS‐GC method is 0.79 μmol and 1 %, respectively.

Heat effects in the reaction of sulfuric acid with ilmenites influenced by initial temperature and acid concentration

Abstract The influence of temperature and sulfuric acid concentration on the enthalpy and the rate of heat release during the reaction of Norwegian and Australian ilmenites with sulfuric acid was determined. The experimental results obtained from calorimetric measurements were compared with theoretical calculations based on the oxide composition and the phase composition of the raw material. Experimentally determined heat of reaction for Norwegian ilmenite (900–940 kJ/kg) and Australian ilmenite (800–840 kJ/kg) showed good agreement with theoretical calculations based on the phase composition of the raw material. It was found that the enthalpy of ilmenites decomposition reaction does not depend on the concentration of sulfuric acid in the concentration range from 83% to 93%. It was also demonstrated that the temperature and concentration of sulfuric acid have a significant impact on the thermokinetics of the decomposition process, increasing the value of the average rate of temperature change.

The Study of Rice Shell Ash Precipitation Legal System for Silica

Using rice husk ash as raw material, low modulus sodium silicate was prepared and high dispersion white carbon black was prepared by chemical precipitation method. The effects of sulfuric acid concentration, reaction temperature and aging time on the oil absorption value (DBP). The high dispersion white carbon black was characterized by laser particle size analyzer, X-ray diffractometer, DBP and scanning electron microscope (SEM). The results show that when the sulfuric acid concentration is 5%, the temperature is 85°C, and the aging time is 60min, the silica morphology is spherical, and the average particle size is about 5 micron, the oil absorption value is 2.82.

New Mechanistic Pathways for the Reactions of Formaldehyde with Formic Acid Catalyzed by Sulfuric Acid and Formaldehyde with Sulfuric Acid Catalyzed by Formic Acid: Formation of Potential Secondary Organic Aerosol Precursors

Formaldehyde (HCHO) plays an important role in the formation of secondary organic aerosols. Here, we report new mechanistic pathways for the reactions of formaldehyde with formic acid catalyzed by sulfuric acid and formaldehyde with sulfuric acid catalyzed by formic acid by using quantum chemical methods and reaction rate theory. We have found that sulfuric acid and formic acid have a strong catalytic role in the HCHO···HCOOH + H2SO4 and HCHO···H2SO4 + HCOOH reactions because the calculated energy barriers of the sulfuric acid-catalyzed reaction of formaldehyde with formic acid and formic acid-catalyzed reaction of formaldehyde with sulfuric acid are decreased by 21.17 and 14.81 kcal/mol, respectively. The calculated rates show that the reaction rate of HCHO···HCOOH + H2SO4 is faster than those of HCHO···H2SO4 + HCOOH and HCHO + HCOOH···H2SO4. Moreover, the HCHO + HCOOH + H2SO4 → H2C(OH)OCOH + H2SO4 reaction readily forms the carboxylic acid ester (H2C(OH)OCOH); this is a new mechanistic pathway for the reaction of formaldehyde with formic acid, which is expected to extend to other aldehydes’ reaction with carboxylic acids. Additionally, the present findings also suggest that formic acid-catalyzed formaldehyde and sulfuric acid reaction leads to the formation of an organosulfate as the nucleation precursor. The present results not only help understand the mechanisms for the initial processes of atmospheric nucleation but also are expected to extend other aldehydes and acids in the atmosphere.

New Insights into the Oxidation Mechanism of Pyrite in Copper-Containing Sulfuric Acid: An Electrochemical, AFM, Raman Spectroscopy and XPS Investigation

The oxidation of pyrite in copper-containing sulfuric acid has been the subject of intense research yet has no comprehensive research on electrochemistry and surface species. In this study, pyrite’s electrochemical oxidation mechanism was systematically elucidated in copper-containing sulfuric acid by using electrochemical techniques. Anodic processes occurring in active, passive, and transpassive dissolution regions were studied by linear sweep voltammetry. The corresponding equivalent electrochemical circuits were fitted for these three regions with the potential of ranging from 0.40 V to 0.80 V vs SCE, and the results of fittings were used to clarify the characteristics of electrodes and electrochemical reactions in copper-containing sulfuric acid. With increasing potential, the reactions on the pyrite surface accelerated, and its roughness significantly increased. In addition, the interfacial transfer of electrons is dominated by surface charge transfer. The products of pyrite surface oxidation were identified by Raman spectroscopy and X-ray photoelectron spectroscopy. Based on the results of the electrochemical methods and surface analysis techniques, the mechanism of pyrite oxidation can be clarified and the specific course of the reaction can be described in detail. These results provided further insight into a better understanding of the pyrite oxidation mechanism in the presence of copper ions.

Process Optimization for Biodiesel Production from Highly Acidic Hibiscus Cannabinus (Deccan Hemp) Oil

In this study, Hibiscus Cannabinus (deccan hemp) oil was used to convert its methyl ester. Methyl ester synthesis process involves of two-steps: esterification of sulfuric acid (Step-1) and alkaline transesterification (Step-2). Deccan hemp oil was found to have an initial acid value of 12.48 mg KOH/g. The acid value of deccan hemp oil was decreased to below 2 mg KOH/g in Step-1 taking consideration to get higher ester yield after alkaline transesterification process. The alkaline transesterification process parameters such as methyl alcohol to deccan hemp oil molar ratio, sulfuric acid catalyst amount, reaction temperature and reaction time were optimised and analysed in detail. This process gives ester yield of about 95.48%. The important properties of the synthesised methyl ester were determined and compared with IS 51607 and ASTM D6751 biodiesel standards.

Corrosion mechanism and degradation behavior of basalt fiber-reinforced composites in sulfuric acid solution

Epoxy resins reinforced by basalt fibers were treated with a sulfuric acid solution for different periods and concentrations. The tensile strength of the composites was examined after the treatment. The fracture surfaces were characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The tensile strengths of the sulfuric acid solution-treated samples showed a decreasing trend with treating times and concentrations. However, after 250–500 h of treatment time, the tensile strengths showed an increasing trend. Based on the experimental results, the possible corrosion mechanisms were explored. Sulfuric acid leads to insoluble sulfur oxide formation with high C, Ca and Fe element contents on the fiber surface. With the continuation of sulfuric acid reaction, a thin corrosion shell covers the whole fiber surface. The thickest corrosion shell caused a significant increase in the tensile strength at the breaking of basalt fibers.

Synthesis, structure elucidation, vibrational and thermal behavior study of new one-core dication molten-salt

We decided to conduct the acid-base reaction of piperazine and sulfuric acid as a secondary diamine and diprotic acid, respectively. A new molten salt was obtained, which its structure elucidation was performed by FTIR, 1D NMR, 2D NMR, and mass spectrometry. In contrast to previous reports and our expectation, no characteristic signal was detected for the existence of hydrogen sulfate anion in 1H NMR of molten salt in DMSO‑d6. The 1H NMR of reactants, the new molten salt, and another derivative of this molten salt analyzed in the same deuterated solvent. Further support for the formation of 1H,4H-piperazine-N,N'-diium dication was concluded by an NMR study of its bromide derivative i.e., 1H,4H-piperazine-N,N'-diium dibromide. Based on the results of FTIR, NMR, pH, and titrimetry analyses, the formation of sulfate anion and the presence of an excess of sulfuric acid were excluded. The thermal behavior and thermal stability of new molten salt are also studied and reported.

Bacterial cellulose production by Acetobacter xylinum CGMCC 1.2378 using coconut shell acid hydrolysate as carbon source

Bacterial cellulose (BC) was synthesized by Acetobacter xylinum using a carbon source of coconut shell hydrolysate, which was treated with an ultra-low concentration of sulfuric acid. The coconut shell was found to contain 57.13% holocellulose and 27.42% lignin. The effect of sulfuric acid concentration, reaction temperature, and reaction time on hydrolysis of coconut shell were evaluated by response surface methodology. The reducing sugar concentration was 8.39 g/L under the predicted optimum treatment at 200 °C for 32 min with a solution of 0.07% sulfuric acid. The holocellulose conversion rate was 56.1% at this condition. In a detoxification process using calcium hydroxide and activated carbon, furfural and hydroxymethylfurfural in the hydrolysate were almost completely removed, whereas formic acid and acetic acid levels decreased by 30%. After cultivation for 7 days at the reducing sugar status of 5 g/L, the BC production in medium with the detoxified hydrolysate could reach 1.66 g/L. After fermentation for 21 days, BC yield in medium using composited carbon source (20 g/L) of glucose and hydrolysate was 5.30 g/L. Structural analysis showed that BC obtained from medium of control and detoxified hydrolysate exhibited similar properties. This work provided a potential method for BC production.

Gamma - Radiation-induced reaction of Sulfuric Acid with Silica gel: A Novel method for the formation of sulfonic acid - functionalized silica (SiO2-SO3H)

Radiation-induced reaction of sulfuric acid with silica gel (SG) was carried out using ɤ-radiation from a 60Co source at room temperature and, its mechanism were suggested. The formation of sulfonated SG (SiO2-SO3H) was confirmed by IR, thermal analysis (TGA/ DSC). Elemental analysis and morphological structure of treated SG (SGtreated) was investigated by scanning electron microscopy (SEM). According to the comparison of the SEM images of SG and SGtreated , it seems that, irradiation of SG in the presence of sulfuric acid leads to partial segmentation of SG particles. The IR spectra of the treated silica (SGtreated) is different from that of the SG. Where, peaks related to the presence of sulfunic group are observed, as well as shifts of SG peaks due to treatment. Also, TGA/ DSC of SGtreated is different from that of SG. Elemental analysis reveals that particle size of SG affects the S/O % value, where SGtreated with >0.16mm - 0.2mm particle size has the maximum value. Also, S/O% value, of >0.16mm - 0.2mm SG particle size, increased, linearly, with absorbed dose up to 80 kGy and then decresedat higher doses.

Synthesis of anhydrite from red gypsum and acidic wastewater treatment

One-step process of red gypsum leaching to produce anhydrite was proposed. The effects of sulfuric acid concentration, reaction temperature and reaction time on both the leaching rate of red gypsum, the phase and micro-morphology of the product were systematically investigated. The acid leaching solution was tried to use circularly. And the valuable components in the leaching solution were recovered by step precipitation. Anhydrous calcium sulfate powder with anhydrite crystal phase and smooth and serrate morphology was successfully produced. The leaching rate of red gypsum was 39.82% under optimized conditions. The optimum cycle number for the reuse of acid leaching solution was 5. Sulfate ions and iron ions in the leaching solution were recovered by adjusting the pH value. A preparation mechanism of anhydrite from red gypsum was also proposed by theoretical analysis. All of these indicated that the whole procedure setup showed potential application for red gypsum utilization.

Sulfuric acid decomposition in the iodine–Sulfur cycle using heat from a very high temperature gas-cooled reactor

Using the heat of high-temperature gas-cooled reactor to drive the thermochemical iodine-sulfur cycle is an important way to produce hydrogen on a large scale. The sulfuric acid decomposition is the key reaction affecting the hydrogen production efficiency in this method, so efficient sulfuric acid decomposition is needed. The present study focuses on the temperature rise, phase change and chemical reactions of sulfuric acid in a bayonet heat exchanger. The evaporation-condensation model in a steady temperature field was used to simulate the different stages of the phase change process with the species transport model used to calculate the product proportions. Finally, the effects of two catalyst arrangements on the decomposition fraction were analyzed. The results show that the temperature in the catalytic core area reaches 1100 K which provides the heat required for the decomposition reaction. When the sulfuric acid flow rate is 0.36 kg/h, the two-phase flow section is about 0.22 m long to promote better heat transfer. The simulations show that square and circular catalysts give sulfuric acid decomposition fractions of 65% and 57%. The pressure drop of the two catalyst arrangements is almost the same, while the square catalyst has a higher decomposition fraction, which can improve the economics. This study provides a reference for optimizing catalyst selection based on the flow and heat transfer rates.

Kinetics of nickel leaching from low-nickel matte in sulfuric acid solution under atmospheric pressure

In the conventional metal extraction process, copper-nickel sulfide ores are generally treated by pyrometallurgical processes, including smelting and converting operation. The purpose of the smelting process is to eliminate most of the iron and to concentrate the valuable metals, such as nickel, copper and platinum group metals, into a low-nickel matte. Then, the remaining iron is oxidized and fluxed for removal as silicate slag in the converting process, and the low-nickel matte is converted into a high-nickel matte. However, a substantial portion of cobalt is also oxidized and converted into the slag phase. Additionally, the subsequent treatment of the high-nickel matte after the grinding and flotation processes is complicated, and leads to the dispersion of noble metals. Usually, the loss of noble metals is about 10% ~ 20%. Direct treatment of low-nickel matte by hydrometallurgical methods instead of the converting process may be a good choice, which will prevent the loss of associated elements, such as cobalt and noble metals. Since copper has a very strong affinity for sulfur, the sulfides of iron, cobalt and nickel may dissolve into the liquid phase (leach liquor) under controlled the acidity of the solution, whereas the cuprous sulfide should remain in the residue. The inert noble metals should concentrate in the cuprous sulfide. However, a large amount of toxic hydrogen sulfide will be released in the leaching process, which can be converted to elemental sulfur by the Claus process. Based on the above considerations, it is possible to develop a method for extracting valuable metals from low-nickel matte and recovering the associated cobalt and noble metals. In this study, the kinetics of the acid leaching process of low-nickel matte under atmospheric pressure was studied. In addition, the effects of the stirring speed, initial sulfuric acid concentration, reaction temperature and particle size on the leaching of nickel were investigated. The kinetic analysis of the leaching data for various experimental conditions indicated that the reaction was controlled by diffusion through an inert porous layer. It was determined that the reaction order was 0.54 with respect to sulfuric acid with an activation energy of 58.3 kJ mol−1.

Pretreatment and Detoxification of Acid-Treated Wood Hydrolysates for Pyruvate Production by an Engineered Consortium of Escherichia coli.

The biorefinery concept makes use of renewable lignocellulosic biomass to produce commodities sustainably. A synthetic microbial consortium can enable the simultaneous utilization of sugars such as glucose and xylose to produce biochemicals, where each consortium member converts one sugar into the target product. In this study, woody biomass was used to generate glucose and xylose after pretreatment with 20% (w/v) sulfuric acid and 60-min reaction time. We compared several strategies for detoxification with charcoal and sodium borohydride treatments to improve the fermentability of this hydrolysate in a defined medium for the production of the growth-associated product pyruvate. In shake flask culture, the highest pyruvate yield on xylose of 0.8g/g was found using pH6 charcoal-treated hydrolysate. In bioreactor studies, a consortium of two engineered E. coli strains converted the mixture of glucose and xylose in batch studies to 12.8 ± 2.7g/L pyruvate in 13h. These results demonstrate that lignocellulosic biomass as the sole carbon source can be used to produce growth-related products after employing suitable detoxification strategies.

Synthesis of mono- and bis-spirooxindole derivatives "on water" using double salt of aluminum sulfate-sulfuric acid as a reusable catalyst.

The preparation of double salt of aluminum sulfate-sulfuric acid (Al4(SO4)6·(H2SO4)·24H2O) by the reaction of aluminum sulfate and sulfuric acid in water is described. Aluminum sulfate-sulfuric acid is characterized via some spectroscopic and microscopic techniques such as infrared spectroscopy (IR), X-ray diffraction spectroscopy (XRD), energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which corroborated the structure of the double salt. This double salt is soluble in water and insoluble in organic solvents. It was employed as a new catalyst for the synthesis of spirooxindole compounds on water with good to excellent yields. The double salt could be recycled and reused without appreciable loss of activity.

Моделирование влияния растворителя на возможность образования катиона HSO3+

The possibility of describing the reactions of heterolytic dissociation sulfuric acid and the further conversion of the H3SO4+ cation to HSO3+ by the density functional theory method was studied. By comparing with the calculated and experimental data, a functional and a basic set were selected for modeling these reactions. The influence of the solvent on the course of the studied reactions was studied: based on COSMO continuum model (implicit solvent accounting) and explicit solvent accounting (introduction of particles participating in the reaction into the solvation shell of four sulfuric acid molecules). It was shown that individually neither the continuum model nor the explicit solvent accounting can adequately describe the reactions under study from the aspect of energy effects. It was determined that the reactions studied can occur only in strongly polar solvents. The effect of the content of sulfuric trioxide in oleum on the particle formation energy of H3SO4+ and HSO3+ was studied. It was shown that an increase in the concentration of sulfuric trioxide from 0 to 15% reduces the energy spent on the formation of H3SO4+ and HSO3+ particles by 2.5 and 3.5 kJ/mol, which leads to an increase in the equilibrium constants of the formation reactions of these products by 2.74 and 4.11 times. An approximate estimate is made of the equilibrium constant of the reaction of formation of the HSO3+ cation, equal to ~10-7-10-8. It was shown that particles of HSO3+ and SO3 in sulfuric acid solutions exist in the form of associates with sulfuric acid, through the sulfur atom SO3/HSO3+ and oxygen H2SO4, in which the S···O distance is 1.98 Å for SO3 and 1.9 Å for HSO3+.

H-Pyrr][HSO4] as an Efficient Ionic Liquid Catalyst for the Synthesis of Xanthenes, Tetraketones, and Triazolo[2,1-b]quinazolinones

Pyrrolidin-1-ium hydrogen sulfate ([H-Pyrr][HSO4]) was prepared by a simple and atom-economic neutralization reaction of sulfuric acid and pyrrolidine. This reagent can be used as an easily available, cheap, recyclable, and environmentally benign catalyst for the promotion of the synthesis of 1,8-dioxo-octahydro-xanthenes, tetraketones, and triazolo[2,1-b]quinazolinone derivatives. Easy preparation of the catalyst, simple work-up procedure, green process, high yields, and short reaction times are the most important advantages of this method.

Effect of sulfuric acid reaction time on the properties and behavior of cellulose nanocrystals from Cocos nucifera var-Aurantiaca peduncle’s cellulose microfibers

Cocos nucifera var-Aurantiaca peduncles are agricultural waste material discarded by harvesters after taking the fruit. The isolation of Cellulose NanoCrystals (CNCs) from peduncle derived Cellulose MicroFibers (CMFs) is an effective alternative approach to recover the waste. In the present work, CNCs were isolated by using sulfuric acid hydrolysis (64 wt%) with different hydrolysis time at constant temperature of 45 °C. The effect of hydrolysis time (30, 45, 60 min) on the crystalline index, colloidal stability of suspension, yield, thermal stability, morphology, chemical and elemental composition of CNCs are evaluated. The characterization of isolated CNCs with 60 min (CNCs/60 min) hydrolysis time provides high crystalline index (%), yield (%) with good colloidal stability and appearance in well dispersed uniform rod-like structure with a width of 12 ± 1.2 nm and length of 200 ± 20 nm. The effect of reinforcement of CNCs/60 min in agar matrix whose tensile strength is increased by 37% when 6 wt% of CNCs/60 min was loaded into the matrix.

Alkaline hydrogen peroxide-pretreated sugarcane tops for bioethanol production—a process optimization study

In the present work, sugarcane tops (SCT), an agricultural residue, were subjected to alkaline hydrogen peroxide (AHP) subsequently followed by acid hydrolysis for the maximum release of fermentable sugars for bioethanol production. The process parameters that affect the AHP pretreatment efficiency include AHP concentration (%, v/v), SCT loading (%, w/v), pretreatment time (h), pretreatment temperature (°C), and agitation speed (rpm) were studied for effective delignification. Furthermore, central composite design (CCD) based on response surface methodology (RSM) was applied for optimizing various process parameters of acid hydrolysis such as sulfuric acid concentration (%, v/v), reaction time (min), and reaction temperature (°C). The optimal hydrolysis conditions yielded 6.911 g/L of xylose and 4.106 g/L of glucose. The hydrolyzate containing fermentable sugars was fermented using Saccharomyces cerevisiae, and about 9.9 vol% ethanol was obtained at the end of 24 h fermentation. The native, pretreated, and hydrolyzed SCT were also characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques.